Impact tool



Jan 30, 1951 F. H. THoMAs i 42,539,678 .IMPACT Toor. l

Filed Aug. 31, 1945 lNVEN'I'OR H'S ATTORNEY.

Patented Jan. 30, 1951 IMPACT rOOL Floyd H. Thomas, Milan, Pa., assignor to Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application August 31, 1945, Serial No. 613,814

Claims.

This invention relates to impact tools and more particularly to impact wrenches and similar tools in which a rotating element strikes blows to rotate a spindle carrying a tool such as a socket wrench or the like.

In instruments of this character there is generally provided an anvil member to receive blows to be struck by a, rotating hammer, and a certain amount of the force of the hammer is lost due to looseness or play between the anvil and the part which it is proposed to turn. A great increase in effectiveness is obtained if this looseness can be eliminated.

It is accordingly an object of this invention to maintain sufficient torque at the anvil to prevent the looseness or play above referred to. This is accomplished in its preferred embodiment by providing a member positively connected to the anvil and frictionally associated with the drive shaft of the machine so that rotation of the driver tends to rotate the anvil in the desired direction of rotation.

Further objects and advantages of the invention will be in part obvious and in part pointed out hereinafter.

1n the drawing in which similar parts are designated by similar reference character,

Fig. 1 is a longitudinal section thru a part of an impact wrench constructed in accordance with the practice of the invention.

Fig. 2 is a section of the wrench of Fig. l taken along the line 2-2 looking in the direction of the arrows.

Fig. 3 is a fragmental longitudinal view of a modification of the invention showing a modified form of a connecting member associating the driver and the anvil, and

Fig. 4 is a cross section taken at the line 4-4 of Fig. 3 looking in the direction of the arrows.

Referring to the drawings and more particularly to Figs. 1 and 2 there is illustrated an impact wrench shown in position for driving a nut i6 on a bolt lI. In the view shown the motor and gearing end of the machine is not illustrated, not being part of the invention. The wrench comprises a casing I2 within which is suitably journalled a drive shaft I3 which is adapted to rotate the hammer element I4 for striking the anvil I5. Casing I2 is provided with a suitable front housing I6 for the hammer I4 and anvil I5. The housing I6 is secured to the forward end of the casing l2 by bolts I'I and nuts I3. The anvil I5 is provided with a bearing I9 in the nose of the housing I6 and is adapted to extend beyond the housing being provided with a square end 2Q 2 for attachment to a suitable tool, in this instance a socket wrench 2l fitting the nut IIJ.

Means is provided to convert the continuous rotation of the shaft I3 into intermittent rotation of the hammer element I4 and to this end there is provided a cup shaped cam member 22 having V-shaped grooves 23 in its outer surface to accommodate balls 24 which ride also in oppositely disposed V-shaped grooves 25 on the interior surface of the hammer I4. The object of the grooves 23 and 25 and the balls 24 is to withdraw the hammer I4 in a longitudinal direction from the anvil I5. This is normally opposed by the compressive force of a coil spring 26 tending to force apart the hammer I4 and the cam member 22 so that the balls 24 will normally rest in the apices of the grooves 23 and 25. Cam member 22 is provided with a hexagonal hole 2'! fitting the hexagonal portion 28 of the shaft I3. The hammer i4 is guided centrally by a shaft or stem 29 having a bore 39 to receive the reduced end 3| of the drive shaft I3. At its other end the shaft 29 is provided with a cylindrical portion 32 rotatably tting within the longitudinal bore 33 of anvil I5.

Adjacent the shaft I3, the stem 29 is provided with a iiange 34 flatly seated within the cupshaped cam member 22 and frictionally engaging it so that there is a tendency of the two to rotate together. Flange 34 also serves as part of a thrust bearing comprising race 35 and balls 36, v

v which thrust bearing is adapted to transmit the compression of the spring 26 to push the cam member 22 and hammer I4 apart. At its forward end the hammer I4 is provided with striking faces 38 cooperative with corresponding projections 40 on the anvil I5.

The operation of the hammer and anvil with respect to each other is according to the invention described in Jimerson and Reynolds Patent #2,160,150 of May 30, 1939. When the resistance of the rotation to the anvil I5 becomes suicient the hammer I4 is unable to rotate until withdrawn from engagement-therewith by the cam action of the grooves 23 and 25 and balls 24. The rotation of the drive shaft I3 will cause the balls to ride up in the grooves 23 and down into the grooves` 25 compressing the spring 26 and storing energy therein. When the hammer has been withdrawn so that the striking faces 38 dis- 'engage the projections 40 of the anvil the hamrner 54 is free to rotate. Upon being released its speed is increased beyond the rotational speed of the shaft i3, the energy stored up in the spring 26 ibeing then transmitted to the hammer to provide the increased velocity. As the hammer I4 rotates ahead of the shaft I3 it again moves forwardly so that its striking faces 38 are in position to strike the projections 40 of the anvil whereupon the action above described is repeated.

Heretofore, when the anvil 'I5 was released from engagement with the hammer I4 the reaction caused play between the square end of the shaft 2D and the socket 2I as well as between the socket 2| and the head of the nut I9. This play or looseness absorbs a considerable degree of energy by striking of the parts together as the anvil I is again struck.

This invention provides means for biasing the anvil I5 in the direction of rotation of the shaft I3. To this end the shaft 29, which frictionally engages the shaft I3 thru the contact of the ange 34 with the interior of the cup-shaped cam member 22, is provided with a hook member 45 which engages the anvil to tend to turn the -anvil I5 in the direction of the hammer I4.

In the embodiment shown in Figs. l and 2 the hook member 45 -on the shaft has la hexagonal -bore 45 fitting the hexagonal portion 4I of stem .29 adjacent the projections 4I) Aof the anvil i5. Exteriorly, the member 45 is cut away as at 43 -to receive the projections 40 and permitting only `a limited motion of the shaft 29 with respect thereto.

`eliminate all slack in the connections to the nut I0.

An alternative arrangement is shown in Figs. 3 and 4 wherein a fork 50 is provided having a hexagonal bore 5I to t the hexagonal portion 4. of shaft 29. Fork 50 is provided with a pair of arms 52 which extend forwardly and engage the fiat :opposed sides of the anvil I5. As shown in Fig. 4 the internal faces of the arms 52 are flattened as at 53 to provide a solid -contact with the faces v54 of the anvil I5. The biasing action of the fork member 52 is similar to that of the hook member 4-5.

In both emodiments the anvil 54 is gripped loosely by the hook member 45 and the fork 5I) so any shock imparted to the anvil 54 by the hammer lllwill inno way be transmitted to the drive shaft I3.

Thus by the above construction are accomplished among others the objects herein before referred to.

I claim:

1. An impact tool comprising an anvil element, a rotatable hammer adapted to strike said anvil element, a driving element for the hammer adapted to rotate constantly, a member frictionally engaging the driving element and positively engaging the anvil element tending to rotate said anvil element in the direction of said hammer and resilient means between the rotatable hammer and said member to maintain such frictional engagement.

2. An impact tool comprising a casing, an anvil rotatably mounted in said casing, a drive shaft ournalled in said casing, a hammer for striking said anvil, means to convert the constant rotation of said shaft into intermittent rotation in the hammer including a member positively connected to said shaft, and a stem fictionally engaging said member and positively engaging said anvil to bias said anvil in the direction of rotation of the hammer.

3. An impact tool comprising a casing, an anvil rotatably mounted in said casing, a drive shaft journalled in said casing, a hammer for striking said anvil, means to convert the constant rotattion of said shaft into intermittent rotation in the hammer, and a member slippingly connected to said drive shaft, positively connected to said anvilv to tend to rotate said anvil and normally tending to press 'said anvil in the direction of rotation of said hammer.

4. An impact tool comprising a casing, an anvil rotatably mounted in said casing, a drive shaft journalled in said casing, a hammer for striking said anvil, vmeans to convert the constant rotation of said shaft into intermittent rotation in the hammer, and a member frictionally driven by said drive shaft and positively transmitting torque to said anvil including a shaft extending through the hammer and acting as a guide therefor.

5. An impact tool comprising an anvil element,

a rotatable hammer adapted to strike said anvil element, a driving element for the hammer adapted to rotate constantly, and a member frictionally engaging the driving element and positively engaging the anvil element to tend to rotate the anvil in the direction of .rotation of the hammer.

FLOYD H. THOMAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,160,150 Jimerson et al May 30, 1939 2,220,711 Fitch Nov. 5, 1940 2,285,638 Amtsberg June 9, 1942 

